hmmm, alright, now I found the source sdk base 2007.gcf as some Rapidshare download (so I can't say for sure if it's even the real deal) and put it into steamapps folder...is that right?
well, now launching the game via the shortcut (there's no exe file in the gesource folder; is that normal? O_o ) I get an error saying "Steam.exe (main exception): Win32 StructuredException at 0040EDB7 : Attempt to write to virtual address 4293517097 without appropriate access rights."
If I put the -novid in, there's no error message, but the game doesn't start either...
this is how it's supposed to look, right? "C:\Program Files (x86)\Steam\Steam.exe" -applaunch 218 -game "C:\Program Files (x86)\Steam\SteamApps\sourcemods\gesource" -novid